1. Field of the Invention
The present invention relates to a method of manufacturing a liquid crystal display apparatus.
2. Description of the Related Art
Conventionally, in a method of manufacturing a liquid crystal display apparatus, a first substrate and a second substrate, which are provided with a plurality of single-element seal members (each of which surrounds a region where a display element is formed), are bonded to each other with the single-element seal members, and then the two glass substrates are etched by soaking them in this state in an etching solution in an etching bath, thereby reducing the thickness of the two glass substrates is reduced (for example, refer to U.S. Pat. No. 6,197,209).
In this conventional manufacturing method, the temperature of the etching solution in the etching bath increases with the degree of progress of etching of the glass substrates, that is, with an increase in etching thickness of the glass substrates (an amount of the thickness of each of the glass substrates that is etched). Therefore, the time of finishing the etching, that is, of changing the thickness of the glass substrates to a desired thickness, is determined based on a result of detecting the temperature of the etching solution in the etching bath.
In this case, the etching speed depends on the temperature and the concentration of the etching solution in the etching bath. Therefore, if the initial temperature and the initial concentration of the etching solution vary, the temperature of the etching solution at the etching-finishing time, when the glass substrates have a desired thickness, varies.
Further, general methods of manufacturing a liquid crystal display usually adopt a process in which an assembly is made by bonding two glass substrates, which have an area where a plurality of finished liquid crystal display apparatuses can be formed, with a plurality of single-element seal members, and batch processing is performed for a plurality of assemblies to increase productivity, by etching the plurality of assemblies simultaneously by soaking the assemblies in an etching solution in an etching bath.
In such batch processing, the increase in temperature of the etching solution in the etching bath with the progress of etching varies according to the number of batched assemblies soaked in the etching solution, and thus the temperature of the etching solution at the etching finishing time, when the glass substrates have a desired thickness, varies.
As described above, the temperature of the etching solution in the etching bath at the etching finishing time when the glass substrates have a desired thickness varies according to the initial temperature and the initial concentration of the etching solution and according to the number of batched assemblies. Therefore, preliminary experiments are performed according to these parameters, and the temperature of the etching solution at the etching finishing time is determined based on a result of the preliminary experiments.
The total number of parameters such as the initial temperature and the initial concentration of the etching solution and the number of batched assemblies is equal to the product of the numbers of individual independent parameters. Therefore, when the conventional technique described above is carried out, it is necessary to perform a large number of preliminary experiments, and an enormous amount of work is required. Further, the relationship between the temperature of the etching solution and the etching thickness of the glass substrates varies according to variation in the volume of the etching bath to be used and a change in the amount of etching solution to be used from the amount in the preliminary experiments. Thus, it is necessary to perform the above large number of preliminary experiments for each etching apparatus, requiring still more preliminary work.
Moreover, the surfaces of glass substrates originally have projections and depressions of an order of 1 μm or less. Therefore, only reducing the thickness of two glass substrates by etching increases projections and depressions of the order of 1 μm or less which originally exist on the surfaces of the glass substrates to relatively large projections and depressions of μm order. Therefore, reducing the thickness of the glass substrates causes cracking due to the relatively large projections and depression of μm order, and thus the glass substrates easily crack.